Tech Controllers ST-979 User Manual

ST-979 user’s manual
23
 Operation modes
The controller may supervise the CH boilers operation in one of the two modes: weather-based
control (control based on external temperature value) and modulation (control based on the pre-
set CH boiler temperature).
NOTE
CH temperature and external temperature is sent only from the boiler connected to
socket no 1 (the first one on the left).
 Weather-based control
In this mode the CH boilers operation is controlled on the basis of the external temperature value.
The user defines the number of boilers activated at a particular temperature using the following
parameters: Boilers 3 switch-on temperature, Boilers 2 switch-on temperature, Boiler 1 switch-
on temperature and Hysteresis.
Boiler activation in the case of external temperature decrease:
Number
of boilers
active
1
Operates regardless of the external temperature
2
Activated when the external temperature drops to the level defined in Boiler 1
activation temperature minus Hysteresis value.
3
Activated when the external temperature drops to the level defined in Boiler 2
activation temperature minus Hysteresis value.
4
Activated when the external temperature drops to the level defined in Boiler 3
activation temperature minus Hysteresis value.
Boiler deactivation in the case of external temperature increase:
Number
of boilers
active
4
Deactivated when the external temperature reaches the value of Boilers 3
activation temperature.
3
Deactivated when the external temperature reaches the value of Boilers 2
activation temperature.
2
Deactivated when the external temperature reaches the value of Boiler 1 activation
temperature.
1
Operates regardless of the external temperature.
Example:
Boiler 1 activation temperature: 5⁰C
Boilers 2 activation temperature: 0⁰C
Boilers 3 activation temperature: -5⁰C
The following graph illustrates the activation process of the boilers operating according to the
external temperature value:

Tech Controllers ST-979 Specifications

General

Brand	Tech Controllers
Model	ST-979
Category	Controller
Language	English